Field of the Invention
Embodiments of the present invention relate to a liquid crystal display device (LCD) including a nanocapsule liquid crystal layer.
Discussion of the Related Art
Liquid crystal displays (LCDs), which are widely used for TV (television), monitor or the like because of advantage in display moving images and high contrast ratio, displays images through image display principle by optical anisotropy and polarization of liquid crystals.
An LCD includes a liquid crystal panel as a main component which is manufactured by coupling two substrates with a liquid crystal layer therebetween, and changes alignment of liquid crystal molecules by an electric field and displays difference of transmittance.
The liquid crystal panel requires a light source, and so a backlight is located below the liquid crystal panel.
FIG. 1 is a cross-sectional view illustrating an LCD according to a related art.
Referring to FIG. 1, the LCD includes a liquid crystal panel 10 including an array substrate, a color filter substrate and a liquid crystal layer 50 between the array substrate and the color filter substrate, and a backlight unit 60 below the liquid crystal panel 10. A first substrate 2 referred to as the array substrate includes a pixel region P, and on an inner surface of the first substrate 2, a thin film transistor T is in each pixel region P and connected to a pixel electrode 28 in each pixel region P.
On an inner surface of a second substrate 4 referred to as the color filter substrate, a black matrix 32 is formed in a lattice shape surrounding the pixel region P to cover a non-display element such as the thin film transistor T and exposes the pixel electrode 28.
Red, green and blue color filters 34 are formed in the lattice shape corresponding to the respective pixel regions P, and a common electrode 36 is formed on the black matrix 32 and the color filters 34.
First and second polarizing plates 20 and 30 are attached onto outer surfaces of the first and second substrates 2 and 4, respectively.
First and second alignment layers 31a and 31b are formed between both the pixel electrode 28 and the common electrode 36, and the liquid crystal layer 50. The first and second alignment layers 31a and 31b are rubbed and align liquid crystal molecules.
A seal pattern 70 is formed between and along peripheral regions of the first and second substrates 2 and 4 and prevents leakage of the liquid crystal.
The backlight unit 60 is located below the liquid crystal panel 10 and supplies light to the liquid crystal panel 10.
Recently, in order to provide an LCD having an improved response speed, an LCD including a nanocapsule liquid crystal, in which nematic liquid crystal molecules are capsuled by a nanocapsule, have been actively researched.
Since the nanocapsule liquid crystal layer does not need initial alignment, the alignment layers are not required and thus an alignment process such as rubbing is not required.
Further, since the nanocapsule liquid crystal layer is formed to be hardened, when the color filters and the common electrode are formed on the first substrate, the second substrate can be eliminated.
Accordingly, a process of forming a gap for an interval for injecting the liquid crystal layer between the first and second substrates can be omitted, and a process of forming the seal pattern to seal the liquid crystal layer is omitted. Thus, production efficiency can be improved.
However, the nanocapsule liquid crystal layer is weak to moisture. Particularly, when the second substrate is omitted, the nanocapsule liquid crystal layer is directly exposed to the outside, thus moisture is penetrated into the nanocapsule liquid crystal layer, and thus reliability of the LCD including the nanocapsule liquid crystal layer is reduced.
When the reliability is reduced, voltage holding ratio is also reduced. Due to the reduction of the voltage holding ratio, a time to maintain position of a liquid crystal molecule transmitting light is reduced, and thus light transmittance is reduced. This causes reduction of overall brightness of the LCD, or a flicker phenomenon.